Drosophila melanogaster γ-TuRC is dispensable for targeting γ-tubulin to the centrosome and microtubule nucleation

In metazoans, γ-tubulin acts within two main complexes, γ-tubulin small complexes (γ-TuSCs) and γ-tubulin ring complexes (γ-TuRCs). In higher eukaryotes, it is assumed that microtubule nucleation at the centrosome depends on γ-TuRCs, but the role of γ-TuRC components remains undefined

γ-Tubulin ring complexes regulate microtubule plus end dynamics

Independently of their nucleation activity, γ-tubulin ring complex proteins localize along microtubules, limiting catastrophe events during interphase

Fatty acid oxidation of alternatively activated macrophages prevents foam cell formation, but Mycobacterium tuberculosis counteracts this process via HIF-1α activation

The ability of Mycobacterium tuberculosis (Mtb) to persist inside host cells relies on metabolic adaptation, like the accumulation of lipid bodies (LBs) in the so-called foamy macrophages (FM), which are favorable to Mtb. The activation state of macrophages is tightly associated to different metabolic pathways, such as lipid metabolism, but whether differentiation towards FM differs between the macrophage activation profiles remains unclear. Here, we aimed to elucidate whether distinct macrophage activation states exposed to a tuberculosis-associated microenvironment or directly infected with Mtb can form FM. We showed that the triggering of signal transducer and activator of transcription 6 (STAT6) in interleukin (IL)-4-activated human macrophages (M(IL-4)) prevents FM formation induced by pleural effusion from patients with tuberculosis. In these cells, LBs are disrupted by lipolysis, and the released fatty acids enter the β-oxidation (FAO) pathway fueling the generation of ATP in mitochondria. Accordingly, murine alveolar macrophages, which exhibit a predominant FAO metabolism, are less prone to become FM than bone marrow derived-macrophages. Interestingly, direct infection of M(IL-4) macrophages with Mtb results in the establishment of aerobic glycolytic pathway and FM formation, which could be prevented by FAO activation or inhibition of the hypoxia-inducible factor 1-alpha (HIF-1α)-induced glycolytic pathway. In conclusion, our results demonstrate that Mtb has a remarkable capacity to induce FM formation through the rewiring of metabolic pathways in human macrophages, including the STAT6-driven alternatively activated program. This study provides key insights into macrophage metabolism and pathogen subversion strategies.Fil: Genoula, Melanie. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia. International Associated Laboratory; ArgentinaFil: Marin Franco, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia. International Associated Laboratory; ArgentinaFil: Maio, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Dolotowicz, Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Ferreyra Compagnucci, Malena María. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Milillo, María Ayelén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Mascarau, Rémi. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Moraña, Eduardo José. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Palmero, Domingo Juan. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Matteo, Mario José. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Tisioneumonología "raúl F. Vaccarezza".; ArgentinaFil: Fuentes, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: López, Beatriz. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud "Dr. C. G. Malbrán"; ArgentinaFil: Barrionuevo, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Neyrolles, Olivier. International Associated Laboratory; Argentina. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; FranciaFil: Cougoule, Céline. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia. International Associated Laboratory; ArgentinaFil: Lugo Villarino, Geanncarlo. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia. International Associated Laboratory; ArgentinaFil: Vérollet, Christel. Centre National de la Recherche Scientifique; Francia. International Associated Laboratory; Argentina. Université de Toulouse; FranciaFil: Sasiain, María del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia. International Associated Laboratory; ArgentinaFil: Balboa, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentina. Centre National de la Recherche Scientifique; Francia. International Associated Laboratory; Argentin

Hck contributes to bone homeostasis by controlling the recruitment of osteoclast precursors

ABSTRACT In osteoclasts, Src controls podosome organization and bone degradation, which leads to an osteopetrotic phenotype in src ؊/؊ mice. Since this phenotype was even more severe in src ؊/؊ hck ؊/؊ mice, we examined the individual contribution of Hck in bone homeostasis. Compared to wt mice, hck ؊/؊ mice exhibited an osteopetrotic phenotype characterized by an increased density of trabecular bone and decreased bone degradation, although osteoclastogenesis was not impaired. Podosome organization and matrix degradation were found to be defective in hck ؊/؊ osteoclast precursors (preosteoclast) but were normal in mature hck ؊/؊ osteoclasts, probably through compensation by Src, which was specifically overexpressed in mature osteoclasts. As a consequence of podosome defects, the 3-dimensional migration of hck ؊/؊ preosteoclasts was strongly affected in vitro. In vivo, this translated by altered bone homing of preosteoclasts in hck ؊/؊ mice: in metatarsals of 1-wk-old mice, when bone formation strongly depends on the recruitment of these cells, reduced numbers of osteoclasts and abnormal developing trabecular bone were observed. This phenotype was still detectable in adults. In summmary, Hck is one of the very few effectors of preosteoclast recruitment described to date and thereby plays a critical role in bone remodeling.-Vérollet, C., Gallois, A., Dacquin, R., Lastrucci, C., Pandruvada, S. M. N., Ortega, N., Poincloux, R., Behar, A., Cougoule, C., Lowell, C., Al Saati, T., Jurdic, P., Maridonneau-Parini, I. Hck contributes to bone homeostasis by controlling the recruitment of osteoclast precursors. FASEB J. 27, 3608 -3618 (2013). www.fasebj.org Key Words: osteopetrosis ⅐ cell migration ⅐ podosomes ⅐ Src tyrosine kinases Bone is renewed continuously by a process known as bone remodeling. Bone remodeling is accomplished by 3 cell types: osteocytes, osteoblasts, and osteoclasts (OCs). Osteocytes are the mechanical sensors of bone that regulate osteoclast formation. Osteoblasts synthetize the matrix and promote its mineralization, while OCs are responsible for degradation of bones during bone development, homeostasis, and repair. The formation and degradation of bone are tightly balanced in both time and space. A dysregulation of this tight balance between bone formation and bone degradation may result either in loss of bone mass, such as in osteoporosis, or in contrast, in a progressive increase in bone mass, such as in osteopetrosis. Degrading OCs are large multinucleated giant cells formed by the differentiation and fusion of mononuclear monocyte lineage precursors after stimulation by receptor activator of nuclear factor -B ligand (RANKL) and macrophage colony-stimulationg factor (M-CSF) (1-3). They are characterized by high levels of cathepsin K and tartrate resistant acidic phosphatase (TRAP) activities, whic

Dissemination of <i>Mycobacterium tuberculosis</i> is associated to a <i>SIGLEC1</i> null variant that limits antigen exchange via trafficking extracellular vesicles

The identification of individuals with null alleles enables studying how the loss of gene function affects infection. We previously described a non‐functional variant in SIGLEC1, which encodes the myeloid‐cell receptor Siglec‐1/CD169 implicated in HIV‐1 cell‐to‐cell transmission. Here we report a significant association between the SIGLEC1 null variant and extrapulmonary dissemination of Mycobacterium tuberculosis (Mtb) in two clinical cohorts comprising 6,256 individuals. Local spread of bacteria within the lung is apparent in Mtb‐infected Siglec‐1 knockout mice which, despite having similar bacterial load, developed more extensive lesions compared to wild type mice. We find that Siglec‐1 is necessary to induce antigen presentation through extracellular vesicle uptake. We postulate that lack of Siglec‐1 delays the onset of protective immunity against Mtb by limiting antigen exchange via extracellular vesicles, allowing for an early local spread of mycobacteria that increases the risk for extrapulmonary dissemination

The osteoclast, a target cell for microorganisms

International audienceBone is a highly adaptive tissue with regenerative properties that is subject to numerous diseases. Infection is one of the causes of altered bone homeostasis. Bone infection happens subsequently to bone surgery or to systemic spreading of microorganisms. In addition to osteoblasts, osteoclasts (OCs) also constitute cell targets for pathogens. OCs are multinucleated cells that have the exclusive ability to resorb bone mineral tissue. However, the OC is much more than a bone eater. Beyond its role in the control of bone turnover, the OC is an immune cell that produces and senses inflammatory cytokines, ingests microorganisms and presents antigens. Today, increasing evidence shows that several pathogens use OC as a host cell to grow, generating debilitating bone defects. In this review, we exhaustively inventory the bacteria and viruses that infect OC and report the present knowledge in this topic. We point out that most of the microorganisms enhance the bone resorption activity of OC. We notice that pathogen interactions with the OC require further investigation, in particular to validate the OC as a host cell in vivo and to identify the cellular mechanisms involved in altered bone resorption. Thus, we conclude that the OC is a new cell target for pathogens; this new research area paves the way for new therapeutic strategies in the infections causing bone defects

Tunneling Nanotubes: Intimate Communication between Myeloid Cells

Tunneling nanotubes (TNT) are dynamic connections between cells, which represent a novel route for cell-to-cell communication. A growing body of evidence points TNT towards a role for intercellular exchanges of signals, molecules, organelles, and pathogens, involving them in a diverse array of functions. TNT form among several cell types, including neuronal cells, epithelial cells, and almost all immune cells. In myeloid cells (e.g., macrophages, dendritic cells, and osteoclasts), intercellular communication via TNT contributes to their differentiation and immune functions. Importantly, TNT enable myeloid cells to communicate with a targeted neighboring or distant cell, as well as with other cell types, therefore creating a complex variety of cellular exchanges. TNT also contribute to pathogen spread as they serve as “corridors” from a cell to another. Herein, we addressed the complexity of the definition and in vitro characterization of TNT in innate immune cells, the different processes involved in their formation, and their relevance in vivo. We also assess our current understanding of how TNT participate in immune surveillance and the spread of pathogens, with a particular interest for HIV-1. Overall, despite recent progress in this growing research field, we highlight that further investigation is needed to better unveil the role of TNT in both physiological and pathological conditions